OS X in Elementary School

I am installing about 30 OS X clients in an elementary school.

1. What is the method for locking them down so the students can not change the background image, settings etc.?

2. I have a Mac server and a Win server so I have access to Active Dir and Open Dir. Which should I use for logging on to the machine and what is the process for setting that up?

Thanks!

1. give all students standard accounts, not admin accounts. They will need an admin password to do any real changes. You can further manage user accounts from the Mac server. To configure the Mac server to manage accounts consult the documentation.
Apple - Mac OS X Server Snow Leopard - Resources - Documentation

2. This site should help you out
Cross-Platform Networking Solutions